宁夏海原县地质灾害发育特征及形成机理研究

发布时间：2018-01-17 21:17

本文关键词：宁夏海原县地质灾害发育特征及形成机理研究　出处：《中国地质大学(北京)》2015年硕士论文　论文类型：学位论文

【摘要】：海原县位于宁夏回族自治区南部地区,地层区划大部属秦祁昆地层区,地貌以黄土丘陵为主。黄土丘陵的形成,主要是由流水切割上覆于古近系-新近系基岩之上的第四纪黄土,再经过土壤侵蚀等内、外地质作用,最终形成沟壑纵横,黄土残塬、梁峁齐备的地貌特征。山地是由地壳挤压变形,在褶皱、断裂等构造作用下隆升,后期经风化、剥蚀等外动力地质作用改造而成,所以海原县的地形整体起伏较大。在地质构造运动的作用下,海原县经过清水河、祖历河及其支流的侵蚀切割,形成了现今沟谷众多、梁峁起伏、地面破碎的地貌景观。由于海原县的这种独特地理环境,使之成为地质灾害的高发区和易发区。本论文通过对崩滑流以及不稳定斜坡等地质灾害的分布特点、发育特征和形成机理的综合研究,取得了如下进展:一、海原县境内地表水系发育,沟壑纵横,地形破碎,地貌类型以黄土高原梁峁为主,地质环境条件十分脆弱,水土流失较严重。断裂构造较发育,发生过多次破坏性地震。总体来看,海原县属于地质灾害的高易发区。二、海原县境内的地质灾害多集中在主要河流的支流岸边斜坡上,沿河岸分布;在黄土厚度较大的阴坡集中;在直线型和凸型边坡地段相对集中。从时间上来看,在地质历史时期,滑坡、崩塌多出现在全新世;在人类历史时期,滑坡、崩塌多发生于人类活动频繁时期;在一年之内,滑坡、崩塌在7、8、9这三月内相对集中发生;在构造活动年,1920年的海原大地震时期地质灾害集中出现。三、滑坡、崩塌和不稳定斜坡等地质灾害总体上具有数量多、分布集中的特征。多数滑坡平面形态较完整、厚度不大,如遇降雨易复活;崩塌总体规模较小、但危害性大;不稳定斜坡坡宽跨度大、坡形以凸形坡和直线型坡为主;潜在崩滑地质危害严重。四、导致滑坡崩塌等自然灾害形成的控制因素包括坡体地质结构、坡体形态、地层岩性等;影响因素包括地下水和降雨;主要触发因素是地震,其次是人类工程活动和降雨的双重作用。对滑坡崩塌灾害发生的频度和产生风险具有明显的控制作用的因素还包括黄土的厚度、强度及其下伏新近系泥岩的出露高度,这些因素也决定了斜坡变形破坏的方式和强度。大气降水改变了岩土体的抗剪强度、孔隙水压力、容重和浮托力,创造了崩滑形成的条件;地表水以水流的形式侵蚀岩土体,创造崩滑活动的临空条件;由于地下水活动的润滑作用和软化作用,导致黄土强度降低、改变了坡体应力状态,进而加速了岩土体的变形破坏。地震是地灾的主要诱发因素,降雨造成老滑坡复活,人类不合理工程活动会加剧斜坡形成崩滑地质灾害的危害。
[Abstract]:Haiyuan County is located in the southern region of Ningxia Hui Autonomous region, the stratigraphic division is the Qinqi-Kun stratigraphic area, the landform is mainly loess hilly, loess hilly formation. The Quaternary loess was cut by income, which was overlying the Paleogene and Neogene bedrock, and finally formed gully vertical and horizontal, loess remnant tableland after soil erosion and other internal and external geological processes. The mountainous area is formed by the crustal compression deformation, uplift under the action of fold, fault and so on, after weathering, denudation and other external dynamic geological processes. Under the action of geological tectonic movement, Haiyuan County has been cut by the erosion of Qingshui River, Zuli River and its tributaries, forming a large number of gullies and ridges, ridges and knolls. Because of the unique geographical environment of Haiyuan County, it has become a high incidence area and a prone area for geological disasters. This paper analyzes the distribution characteristics of geological hazards such as landslides and unstable slopes. The development characteristics and formation mechanism of the comprehensive research has made the following progress: first, Haiyuan County surface water system development, gully vertical and horizontal, topographical fragmentation, landform type mainly in the Loess Plateau hilly. The geological environment condition is very fragile, the soil erosion is serious, the fault structure is relatively developed, and many destructive earthquakes have occurred. Generally speaking, Haiyuan County belongs to the high risk area of geological hazards. The geological hazards in Haiyuan County are mostly concentrated on the bank slopes of the main tributaries and distributed along the river banks. It is concentrated in the thick slope of loess. From the point of view of time, in the geological history period, landslides and collapses mostly occurred in Holocene. In the period of human history, landslides and collapses mostly occurred in the period of frequent human activities. Within a year, landslides and collapses were relatively concentrated in March; In the year of tectonic activity, geological hazards occurred mainly during the Haiyuan earthquake in 1920. Third, there are many geological hazards such as landslides, landslides, collapses and unstable slopes as a whole. Most landslide plane form is relatively complete, the thickness is not big, if the rainfall is easy to revive; The overall scale of the collapse is small, but the harm is great; The wide span of unstable slope is large, and the slope shape is mainly convex slope and linear slope. The potential landslide geological hazards are serious. Fourthly, the controlling factors of natural disasters such as landslide collapse include slope geological structure, slope body morphology, stratigraphic lithology, etc. Influencing factors include groundwater and rainfall; The main trigger factor is earthquake, followed by the dual effects of human engineering activities and rainfall. The factors that have significant control over the frequency and risk of landslide collapse disaster include the thickness of loess. The strength and the exposed height of the underlying Neogene mudstone also determine the mode and strength of slope deformation and failure. The precipitation changes the shear strength, pore water pressure, bulk density and floating support of rock and soil. Created the conditions for collapse and slip formation; The surface water erodes the rock and soil mass in the form of water flow and creates the condition of collapse and slip. Because of the lubrication and softening of groundwater activity, the strength of loess decreases, the stress state of slope body is changed, and the deformation and failure of rock and soil are accelerated. Earthquake is the main inducing factor of ground disaster. The old landslide is revived by rainfall, and human unreasonable engineering activities will aggravate the hazards of landslide geological hazard.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P694

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